Adjustment mechanism for hydraulic brakes



Sept 19, 1950 P..c. wlLsoN 2,523,172

ADJUSTMENT MECHANISM FoR HYDRAULIC BRAKES Filed .my 24. 194s l Iig. 1, 1; 30* 23;

Ax Jl A A Je INVENTOR. P LMER CLYDE WILSON Patented Sept. 19, 19.50

ADJUSTMENT MEoHANIsM FOR HYDRAULIC BRAKES Palmer Clyde Wilson, Uniontown, Pa. Application 24, 1948, Serial N o.,4'0,47 3

This application relates to an improvement on an invention described in my abandoned application Serial No. 769,687, lfiled August 20, 1947, relating to Adjustment Mechanism for Hydraulic Brakes? In that application an adjusting mech- Qanism is described forlautomatically andv continuously maintaining brake shoes the correct *distance from cooperating brake drumswhen the j- Y brakes are in the off position so that when applied thefbr-ak'eswill rgive effective braking action.

Broadly speaking, the adjusting mechanism com- 4prises a cylinder and a oating piston'conncted between the master cylinder and the wheel 'cylv'inder'sfcf ahydraulic brake system. Th'e'present applicationurelates to' an improved piston which mayfbe used in such an 'adjusting mechanism and which permits a limited quantity of Iiuid to `pass therethrough in one direction for adjustment purposes `.but provides an .effective seat against any othei1V movement of Iiuid past the piston in eitherdirection. 1 1

"The floating lpiston of my invention` has Oppositely extending cuppedgasketstoprevent a surge of fluid past the peripheryofthe piston in either dirctioni' Normally the piston floats, back and` forth in the adjusting cylinder in which it is positioned without allowing any fluid to escape past the` piston as the brakes are applied and released. However, as the brake shoes wear, additional "fluid must be supplied to the wheel cylinders for `effective braking actionand the*` piston tends t movecloser tor the outlet end of the adjusting :cylinder which is connected to the wheel cylinders. When the piston reaches said end` of the Y i adjusting cylinder, it is necessary to allow some I fluidv from the master cylinder to ow past the piston toward the brake cylinder. For thispur- `vpose I provide passageways through my piston controlled bya valve so that when the oating ,piston is forced against oneend of the adjusting `"cylinder by pressure of uid from the master .cylinder the valve is opened and fluid is per- Initted 'to' .pass the oating piston to the wheel cylinders; These `passageways Vdo not extend straight through the piston but act in conjunctionwith thecupped gaskets `so that when the )foot pedal is pressed down the fluid yforced from the master cylinder may flow past the piston under control of the valve vwithout interference from the gaskets, but when the foot pedal is released vthe fluid forced back from the wheel cylinders under pressure from the brake return springs is Yprevented from iiowing past the` pistonby joneof the gaskets, independently of anyactionof the .valve i Since ihef-fuid Qannoi. rese ihaplsisa e claims. (c1. yen -54.5)

Y and the piston can only move to a limited extent This load is sustained, however, without any leak t in the Iadjusting cylinder, the additional iiuid in the system on the wheel cylinder side of the piston holds the shoes at the proper distance from thc drums.

My piston has the further advantage of being ableV to withstand the tendency of iiuid to escape past the piston when the brakes are suddenly applied. The inertia of the piston tends to make it lag behind the initial surge of iiuid, thus imposing arload on the sealing means of the piston.

past the piston, because one of the gaskets is cupped 'toward the uid to seal the periphery of` the piston, and the valve is biased shut to seal the interior passageways through the piston.

, The valveis only open when'continued pressure on 'the foot pedal forces the piston against the end of the adjusting cylinder connected to the brake cylinder, as described above.

Inv the accompanying drawing, I have illustrated certain present preferred embodiments of my invention, in which' Figure 1 is a vertical section of my brake adjustor with the parts shown in position when the brakes are off;

Figure 2 is a section through the line II-II in Figure 1;

Figure 3 is a vertical section of mybrake adjustor with the parts shown in position when the brakes are applied; s

Figure 4 is a vertical section of a modified form of my invention with the parts shown in position when the brakes are off and Figure 5 is a Vertical section of the modied form of my invention shown in Figure 4, with the parts shown in position when the brakes are applied. I

One form of a brake adjustment mechanism constructed in accordance with my invention is shown in Figures 1-3 and comprises a hollow cylinder Ill closed at one end by a head I I and rat the other end by a head I2 which has a valve seat disk I3 on its inner face. A port I4 in the head I2 opens into a conduit (not shown) from the master cylinder, and a port I5 in the cylinder I0 near the head I I opens into a conduit '(not shown) to thewlieel cylinders. The master cylinder and lthe brakerc'ylinders `are of standard design and thence are not illustrated in the accompanying Y drawing.

3 ingly press against the inner walls of the adjusting cylinder. Each of these gaskets has the characteristic that it will oppose the passage of fluid approaching its cupped side, but will bend and allow the passage of fluid approaching from the other side. The piston I6V has cylindrical end portions or heads IS and 2l) against the backs of the gaskets Il and I8 respectively. The head has an extension 2l in the form of a hollow cylinder and the head I9 has a cylindrical extension 22 which screws part of the way into the hollow interior of the extension 2 I the remainder of said hollow interior forming a cavity 23.V The gaskets I'I and I8 fit around the extension 2| and are separated byra sleeve 24 fitted over theextensionZI. y. Y.

Interior passageways through thepistonconnect the space between the gaskets Il and I8 and the outer face of the piston head I9. Passageways 25 Aextend radially from the cavity 23 through the extension 2l and the sleeve 24, and -an opening i5 extends axially through the piston head I9 and its extension 22 into the cavity 23.

A valve stem 2B extends throughv the opening I9/ and longitudinal grooves 29 and 30 in the valve stem permit iiuid to pass through the opening I9 along the valve stem. A valve 32 mounted onY the valve stem within the cavity 23 controls the passage of uid through the opening I9. Av compression spring 33 extends between the valve 2 and the piston head to bias the valve against the opening i9', and thus to keepY the opening closed except at certain' times as willbelater described.

When valve 32 is closed,'the valve stem 28' lprojects beyond the' piston head I9 in the direction of the cylinder head lI.

WhentheA pressure of fluid from .the master cylinder forces ,the piston head I5 against the cylinderhead II, as shown in Figure 3,-the valvey stem is pushed back into the` piston and the valve 32V is'thereby opened. As shown in Figures 2 and'3, a transverse groove 34 across the outer face of piston head I9 forms .a channelvlfor fluid passing out of theiopening Il toward the port I5 when the head I9 is pressed against the cylinder head*V II.

Air may become trapped between the opposed `gaskets I'I, and I8, when fluid is first fed into the system. This air vmaybe released througha vent 35 having a cap 35. f

The operation of my brake adjustment mechanism shown in Figures 1- 3 is 'as follows: When the brakes are in off position the return springs on the brake shoes tend to force fluid out of the wheel cylinders back into the adjusting cylinder ln through the port I5, thereby forcing the piston toward the port I4 connected to the master cylinder until it reaches the position shown in Figure l. The gasket I8 prevents the escape of uid past the piston toward the port I4, irrespective of the action of valve 32, because the interior passageways through the piston are all on one side of the gasket I8 and do not penetrate the piston head 2]! on which the gasket I8 is mounted. However, piston head 2U is pressed against the valve seat I3 and thus adds another seal against escape of iluid past the piston toward port I4.` The valve 32 is biased' shut by thespring 33 so that a sudden` surge vof fluid fromj the master cylinder will 'not pass yover the lips of gasket I8, through the radial passageways 26 into the cavity 23, and thence out throughthe opening I'I before the Valve can close.

When the foot pedalris depressedthe piston moves toward the port I5 connected to the brake 4 f cylinder, forcing fluid-under pressure into the wheel cylinders and applying the brakes. Upon release of the footpedal, the brake shoe return springs force fluid from the wheel cylinders to the cylinder I0 and return the piston to the position shown in Figure l. During the normal movement of the piston, the valve 32 remains closed and cooperates with the gasket Il in preventing any flow of fluid from the master cylinder past the piston, while the gasket I8 prevents any lflow of uid in the other direction.

The adjusting mechanism of the piston cornes into play when the brake shoes have worn so much that the normal movement of the piston toward the port I5 does not force sufcient fluid into the wheel cylinders to apply the brakes. In

that case continued pressure on the foot pedal will cause the piston to press against the cylinder head II until valve stem 28 is pushed inwardly to open valve 32. Fluid will then flow from the master cylinder through port I4, over the lips of gasket I8, through the radial passageways 2B into the cavity 23, and thence past the open valve 32 through the opening I9 and along the groove 34 to the port I5 and thence to the wheel cylinders. The extra uid supplied through the valve 32 to the wheel cylinders will apply the brakes. When the brakes are released, the .brake shoe return springs force fluid from the wheel cylinders back into the cylinder I0, but the extra uid cannot return through or past the floating piston I6 because of the cupped gasket I8. Therefore when the piston Ihas` moved to the position shown in Figure l, the brake shoes will not move from the drums as much as they did before the extra fluid was added to the wheel cylinders. Decrease in the amount of the return movement of the shoes compensates for wear on the shoes so that normal'clearance is maintained between Ythe shoe and drum surfaces.

In Figures l and 5I have illustrated a modiflcation of my invention whereinthe cupped gas- Thehead 52 has an axial opening 54 therethrough which is closed at the outer end by a screw plug 55. The head 52 is threaded into the cylinder 50 and at its inner end holds a metal disk 55, 'and a valve seat disk 5l against the cylinder. Both disks have central openings, the opening through the abutment disk 56 being smaller in diameter than the opening 54 through the head 52. .A port 58 extends through the head 52 to the opening 54 and connects with the master `*cylinder (not shown) A floating piston El) is positioned within'the adjusting cylinder 50. The piston comprises a cylindrical central portion 6I with cupped gaskets 62 and 53 Yat each en d facing cylinder heads 5I and 52, respectively. The cupped outer edges of the gaskets extend away from each other and yieldingly press against the inner cylindrical surface of the cylinder 50. An opening extends axially into the central portion 6l from its end facing the cylinder head 52, and a member 64 Vis screwed part of the way into'said opening,

leavin'g'a cavity 65 in the interior of the piston.

Radial" passageways 6,6 extend from the cavity E5 through the-member '6I -to the exterior surface injli extends'through the openings in the disks 56 and 1 cylinde r head 5 ;..l v Y Tne'tawst in' sa nts iosen'f 'in the opening 61 so that udmay pass between the piston "cavity65"andthe` interior'of the cylinder adjacent its head 52. valve 1| is mounted on the valve stern between the piston member 64 and the valv 'seat vdisk'51, 'and seals the opening 61 when the spring 68 presses the p iston member 64 toward the valve 1.1;,a`s showninFi'gurel.

Thejoperation of the modined apparatus shown res .4 and 5 maybe summarized asffollowV when' thefoot pedal isreieased the brake shoe return springs force fluid back from the wheel cylinders fandthusV cause the piston to moveiagainst the cylinderhead 52, as shown in Figures. .,The gasket 62prevents any fluid from escaping past the piston toward port 58, irrespective of the action of valve 1 I, as valve 1| and the conduits formed by opening 61, :passageways 66 and cavity 65 are all on the opposite'side of gasket 62 from the uid forced back from the brake cylinder. Moreover, valve 1I is pressed between piston member 64 and valve seat disk v56 by said luidback pressure and thus cooperates with gasket 62 to increase the seal against escape of fluid past the piston toward port 58.

The valve v1| is biased to close opening 61 in order to avoid a surge of uid through that opening from the master cylinder when the brakes are suddenly applied. Gasket 63 cooperates with valve 1| inl preventing escape of .fluid past the piston toward port 53.

f The normal movement of the piston between the cylinder'heads is substantially the same as that described above in the case of the piston 5 comes into play when the normalmovement of the piston toward the port 53 is insufficient to apply'the brakes. In that case the piston will be forced toward cylinder head 5I until nut's 10 engage the disk 56, and then the piston will continue to move against the action of spring 69 while the valve stem 68 is held stationary. In

this way the valve 1| will be separated from piston member V64, and fluid under pressure from the master cylinder will pass through the opening 61 into the cavity 65, and thence out through the passageways `66 and past the gasket y62 toward the port 53 connected to the brake cylshown in Figures 1 3. simnariy, theadjusting mechanism of the piston shown in Figs. 4 and elle. en egtletfer than@ .0i-111.11@ through. Vthe cylinder and apiston1v v sli dable ,therein, 4an im- DlQl/Tepston hellingen. .Opening in 'one end, 2111` Opening in its side, and a passageway for iluid extending between said openings,l .ai c upfgasketV and an'outlet fortheflow of fluid through the cylinder and a` piston"r `s1idable therein, an'improved piston havingan opening in one" end, an openingv in'its s ide, and afpassageway 'for uid extending between" saidv openings, a cup gasket adjacent each vend of the'pi'stomeach :gasket having a vile'xibl'eflange and yieldingly pressing against thejcylinder, said gaskets being positioned with the opening in the side of the piston therebetween, a valve vto control the now o f fluid through the passageway, means biasingthe valve to close said passageway, and'a ,member'c onnected to the valve vand movably `inddI ited on the piston to extend therefrom' so lthat movement of the piston may cause said member to engage a xed portion of the cylinder and .thereby open the valve, said flanges extending in opposite directions and arranged to permit flow from the inlet to the outlet past the valve when opened and one of the anges and to prevent flow from the outlet to the inlet,

3. In an adjustment mechanism for hydraulic brakes having a hollow cylinder with an inlet and an outlet for the flow of fluid through the cylinder and a pi'ston slidable therein, an improved piston having an opening in one end, an opening in its side, and a passageway for fluid extending between said openings, a cup gasket adjacent each end of the piston, each gasket having a exible flange and yieldingly pressing against the cylinder, said gaskets being positioned with the opening in the side of the piston therebetween, a valve to control the flow of uid through the passageway, a springA connected to the valve and a fixed portion of the piston to bias the valve to close said passageway, and a member connected to the valve and movably mounted on .the piston to extend therefrom so that movement of the piston may cause said member to engage a fixed portion of the cylinder and thereby open the valve, said flanges extending in opposite directions and arranged to permit flow from the inlet to the outlet past the valve when opened and one of the flanges and to prevent flow from the outlet to the inlet.

4. In an adjustment mechanism for hydraulic brakes having a hollow cylinder with an inlet and an outlet for the flow of fluid through the cylinder and a piston slidable therein, an improved piston adapted to be positioned in said cylinder, said piston having an opening in the end nearest said outlet, an opening in its side, and a passageway for uid extending between said openings, gaskets on the ends of said piston with the opening in the side of the piston therebetween, said gaskets having flexible flanges and'bei'ng cupped toward each other and yieldingly pressing against the cylinder, a valve to control the flow of iluid through the passageway, and a member connected to the Valve and adapted to engage a xed portion of the cylinder in order to open the valve, said ilanges being arranged to permit flow from the inlet to the outlet past one of the flanges and the valve when open and to prevent flow from the outlet to the inlet.

5. In an adjustment mechanism for hydraulic brakes an improved piston as dened in claim 4 and having means biasing the valve to close the passageway.

6. In an adjustment mechanism for hydraulic brakes an improved piston as defined in claim 4 in which the valve opening member comprises a rod connected to `the valve and extending through said passageway beyond the end of the piston to engage a fixed portion ofthe cylinder when the piston moves toward said outlet.

'7. In an adjustment mechanism forv hydraulic brakes having a hollow cylinderv with an inlet and an outlet for the flow of fluid "through the cylinder and a piston slidable therein, an improved piston having an opening in the end nearest said inlet, an opening in its side, and a passageway for fluid extending between said openings, gaskets on the ends of said piston with the opening in the side of the piston therebetween,Y

said gaskets having iiexible anges and being cupped away from each other and yieldingly pressing against the cylinder, a Valve to control the flowof fluid through the passageway, and a member connected to the Valve and adapted to engage a xed portion of the cylinder in order tor open the valve, said flanges being arranged to permit `flow from the inlet to the outlet past one of the flanges and the Valve when open and to prevent flow from the outlet to the inlet. i 8. In an adjustment mechanism for hydraulic brakes an improved piston as dened in laim '7 and having means biasing the valve to close the passageway.`V` l l 9. In an adjustment mechanism for hydraulic brakes an improved piston as deiined in claim 7 inV which the valve opening member extends through thepassageway towards said inlet and engages a` 'fixed portion on the cylinder when the piston moves in a direction away from said xed portion.

' PALMER CLYDE WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

